1. Field of the Invention
The present invention relates to an extraneous matter removing system for turbine blades, which can remove extraneous matter (fouling) adhering to the surface of turbine stator blades, moving blades, and other structural members belonging to a turbine while the turbine is operated.
2. Description of Related Art
A steam turbine is provided with a plurality of stator blades which are disposed in the circumferential direction of a rotor shaft and moving blades which are disposed on the downstream side of the stator blades and are installed rotatably to a rotor. When the turbine is operated continuously, extraneous matter such as silica-based or sodium-based chemical substances contained in steam reacts to heat or pressure in the turbine, adhering to the surfaces of stator blades, moving blades, and the like, and grows gradually. The component and property of extraneous matter is different between the low-pressure side and the high-pressure side (upstream side and downstream side) of the stator blades and moving blades provided in a plurality of stages. If extraneous matter adheres to the surface of a turbine blade, the shape of turbine blade is changed from its original shape, so that turbine performance is degraded with elapsed time.
Conventionally, water cleaning or mechanical cleaning has been performed to remove extraneous matter adhering to the turbine blades. For water cleaning, there is available a method in which the plant is shut down and the turbine is stopped periodically, and the turbine is cleaned by introducing pure water into the turbine while the turbine is rotated at a very low speed. Also, in the mechanical cleaning method, hard extraneous matter is removed compulsorily by shotblasting or blast honing using fine powder.